Envoy
CVE-2026-26308
HIGH
GHSA-ghc4-35x6-crw5
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessSend HTTP request with duplicate headers
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ExploitEnvoy concatenates values into comma-separated string
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ExecutionRBAC Deny rule bypassed via obscured value
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ImpactAccess unauthorized resource
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization logic validation
MITRE ATT&CK
1 technique across 1 tactic: Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Envoy proxy version prior to 1.37.1, 1.36.5, 1.35.8, or 1.34.13 with RBAC filter enabled and Deny rules configured for HTTP header exact-match validation. |
| Impact | CVSS 7.5 (HIGH). Attack vector: Network. Complexity: High. Privileges required: None. User interaction: None. Public exploit/POC available. |
| Exploit ScenarioDerived | An attacker could exploit this vulnerability to bypass RBAC policies—specifically "Deny" rules—by sending duplicate headers, eff. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Envoy's RBAC filter improperly concatenates duplicate HTTP headers into comma-separated strings instead of validating each value individually, allowing attackers to bypass "Deny" access control policies through header manipulation. This vulnerability affects Envoy versions prior to 1.34.13, 1.35.8, 1.36.5, and 1.37.1, and public exploit code exists. Patches are available for all affected versions.
Earlier versions of this analysis (1)
Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. [CVSS 7.5 HIGH]
RemediationAI
A vendor patch is available — apply it immediately. Fixed in version 1.37.1. Restrict network access to the affected service where possible.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in go
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Classified as CWE-863 (Incorrect Authorization). Affects Envoy. Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies—specifically "Deny" rules—by sending duplicate he
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
Lifecycle Timeline
3DescriptionGitHub Advisory
Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies-specifically "Deny" rules-by sending duplicate headers, effectively obscuring the malicious value from exact-match mechanisms. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.
Executive ViewAI
Envoy proxy deployments are vulnerable to authentication bypass through a logic flaw in the RBAC filter when processing HTTP headers with multiple values, potentially allowing unauthorized access to protected resources. Organizations using Envoy as an API gateway or service mesh component should prioritize patching to prevent threat actors from circumventing access controls.
Apply vendor patch. If patching cannot be immediately deployed: implement WAF rules to reject HTTP requests with duplicate or multiple header values for security-critical headers; enable detailed request logging to detect exploitation attempts; restrict network access to Envoy instances to known trusted sources; disable RBAC filter temporarily if operationally feasible pending patching.
Threat Intelligence Overview
NVD
CVE.org
EPSS
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
Affected Products (CPE)GitHub Advisory
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